Method and apparatus for perforating wells



July 24, 1962 H. B. SCHRAMM METHOD AND APPARATUS FOR PERFORATING WELLS 2 Sheets-Sheet 1 Filed Dec. 26, 1957 INVENTOR. Hniirfi. iaxeam/v July 24, 1962 H. B. SCHRAMM METHOD AND APPARATUS FOR PERFORATING WELLS 2 Sheets-Sheet 2 Filed Dec. 26, 1957 INVENTOR.

Mmey i; fcwenmw 3,045,748 METHOD AND APPARATUS FOR PERFURATING WELLS Harry B. Schramm, Dallas, Tex., assignor, by mesne assignments, to Otis Engineering Corporation, Dallas County, Tex., a corporation of Delaware Filed Dec. 26, 1957, Ser. No. 795,362 12 Claims. (Cl. 166-35) This invention relates to a novel method andapparatus for perforating oil wells.

An object of this invention is to provide a new method and means for the gun perforation of a well, wherein the effective cross-seticonal area of the well tubing is not diminished by reason of the perforating device in the tubing, and wherein the tubing remains open to eliminate any appreciable pressure differential due to tubing restriction when the perforating gun is discharged, thereby protecting the casing, tubing and packers. against damage.

An additional object is to provide a new method and means for connecting the perforator gun and detonator for the first time in the tubing near the area to be perforated, thereby eliminating the possibility of premature discharge of the gun and injury to personnel as is the case if the gun and detonator are connected at the surface of the earth.

A further object is to provide a novel method and means wherein a perforator gun is run and positioned in the well and a detonator is then lowered into the well by wire line and connected to the gun, thereby effecting a considerable saving in electrical cable which would otherwise be required. Another object is to provide means for lock ing the perforator gun in the tubing string until the perforator detonator is attached thereto and then for running the entire assembly out the bottom of the tubing into position for perforation.

Yet another object is to provide a method and means for locating the entire perforator assembly below the tubing string at the time of discharge of the gun and yet for controlling the time of discharge from the surface.

Another object is to provide means for removing the unexpended portion of the assembly from the well after discharge of the gun.

A further object of the invention is to provide a method of perforating an oil well at a predetermined distance below the bottom of the tubing string therein which comprises: suspending a perforator in said tubing string adjacent the bottom thereof; connecting a locator member to said perforator at said predetermined distance thereabove while said perforator is suspended in said tubing string; lowering said locator member and perforator as a unit to below the bottom of said tubing string; raising said locator member into proximity with the bottom of said tubing string; and firing said perforator when the locator member is proximate to the bottom of the tubing string.

Another object is to provide apparatus to carry out the method set forth in the last object.

Other objects and advantages will become apparent in the course of the following detailed description.

In the drawings, forming a part of this application, and in which like parts are designated by like reference numerals throughout the same,

FIGS. 1 through 5 are schematic elevational views illustrating the operation of the invention.

FIG. 6 is a sectional view of the gun hanger assembly, with parts shown in elevation.

FIG. 7 is a sectional view of the prong and detonator assembly, with parts shown in elevation.

FIG. 8 is a sectional view of the pressure switch and locator unit, with parts shown in elevation.

In general, and referring to FIGS. 1 through 5, the method and apparatus of the present invention are applied to an oil well lined with a casing 10 within which is 3,45,743 Patented July 24, 1962 installed, in a conventional manner, a tubing string 11, ex-v tending from the surface of the earth to a point near the bottom of the well and packed off to the casing by packers 12. A landing nipple 13 is connected in the tubing string, preferably near the bottom thereof.

A gun hanger assembly comprising an interconnected extension hanger- 14 and perforator gun 15 is lowered by wire line 16. down through the tubing string and is releasably locked into place in the landing nipple, as shown in FIG. 1. The wire line is then pulled from the well, leaving the gun hanger assembly in place.

A prong hanging tool and detonator 17 is then suspended at a predetermined distance below a pressure switch and locator member 18. and the latter member is lowered down through the tubing string by wire line 16, as in FIG. 2, until the prong hanging tool'connects to the extension hanger '14 and the detonator is connected in detonating engagement with theperforator 15, as illustrated in FIG. 3.

The'extensionhanger 14 is then released from the landing nipple 13. for downward movement therefrom, and the whole assembly is lowered by the wire line 16 until the switch member :18- is below the bottom of the tubing string, as shown in FIG. 4.

The wire line 16' is now pulled upwardly to raise the switch member to approximately the level of the bottom of the tubing string whereat the switch member is actuated to detonate the detonator and fire the perforator gun 15 into the desired portion 19 of the casing, as illustrated in FIG. 5.

After perforation, the entire assembly may be pulled upwardly through the tubing string to the top of the well.

The various units of the assembly will now be described in detail.

The Gun Hanger Assembly As seen in FIG. 6, the gun hanger assembly comprises an interconnected extension hanger 14 and perforator gun 15. The extension hanger 14 is substantially the same as that shown in the U.S. Patent No. 2,798,559, issued to John V. Fredd, and entitled Hanger for Well Tubing Extensions and the Like, and is adapted to be releasably locked into a landing nipple 13 identical to that shown in the above patent.

Since the extension hanger 14 and landing nipple 1 3 are fully described in the above mentioned patent, it will suffice for the purposes of the present invention to point out that the extension hanger 14 comprises a generally tubular mandrel 24 having a pair of keys 25, each biased by a spring 26 for outward movement from the mandrel into an internal annular key groove 27 of the landing nipple 13. Each key 25 also has a lower boss portion 28 fitting into the internal annular key groove 29 of the landing nipple.

A pair of locking dogs 31 is carried by the mandrel 24; the dogs being movable outwardly into an annular internal locking groove 32 of the landing nipple 13 upon downward movement of the expander sleeve 33 with respect to mandrel 24. The upper end of the expander sleeve is undercut at 34 to provide for engagement by a suitable fishing tool.

The extension hanger thus far described is identical to that shown in the above mentioned patent, but has been modified in the following manner. Each key 25 is longitudinally. slotted at 36 to permit a locating lever 37 to pass therethrough, the lever being pivotally mounted at 38 to the key, and biased by spring 39 so that the upper end of the lever will be urged outwardly. The upper end of the lever has a lower face 41 formed thereon, which is complementary to the upwardly facing shoulder 42 formed at the lower end. of the key groove 27. With the extension hanger 14'1anded in the landing nipple 13, as shown in FIG. 6, the engagement of the locating lever face 41 with the shoulder 42 of the landing nipple will prevent further downward movement of the extension hanger.

The lower end 43 of the locating lever 37 inclines downwardly through a slot 44 in the mandrel 24 to project inwardly into the bore 45 of the extension hanger. As may be seen, if a suitable tool is lowered down through the bore 45, the locating levers 37 will be rotated so that the upper end face 41 thereof will be moved from engagement with the landing nipple shoulder 42, to allow downward movement of the extension hanger relative to the landing nipple. Each key 25 is downwardly and inwardly inclined at 46, above the lever 37, so that the key will be cammed inwardly upon engagement with the landing nipple shoulder 42 when the extension hanger is moved downwardly.

A suitable coupling 51, connected at the lower end of the extension hanger 14, threadedly engages a tubular gun connector sub 52, to which is attached a conventional perforator gun 15. I

A circular guide member 53, slidably enclosed within the gun connector sub, is biased upwardly by spring 54 into engagement with an inturned shoulder 55 of the connector sub. Standard prima cord 56, the lower end of which is in contact with the explosive within the perforator gun 15, is led upwardly through the gun connector sub, and terminates at the upper surface of the guide member 53.

Since it is contemplated to use any conventional perforator gun in this invention, it is not believed that a detailed description of the illustrated perforator gun 15 is necessary other than to state that it has a plurality of chambers 57 at spaced intervals along the surface of the gun, each of the chambers containing a bullet and being interconnected with the prima cord 56.

The Prong Hanging Tool and Detonator Referring now to FIG. 7, the prong hanging tool and detonator 17 comprises a collet hanger 61 having a vertical bore therethrough into which is threaded a tubular prong member 62. The upper end of the collet hanger 61 is undercut circumferentially therearound at 63 so as to be engageable by a suitable fishing tool. The lower end of the collet hanger has a plurality of spring fingers 64 depending therefrom, each of said fingers having an upwardly and inwardly sloping hook 65 adapted to engage the periphery of the upper surface of the expander sleeve 33 of the extension hanger 14 and a downwardly and outwardly sloping surface 66 engageable with the undercut portion 34 of said expander sleeve.

The prong member 62 is radially enlarged at 62a to be of a diameter sufiiciently small to pass through the bore 45 of the extension hanger 14 and sufiiciently great as to engage the inwardly projecting portion 43 of the locating levers 37 and pivot these levers out of engagement with the landing nipple shoulder 42.

A conventional electrically operated detonator 67 is disposed within the prong member at the lower end thereof, and insulated connecting wires 68 and 69 extend from the detonator up into the electrical cable 70. The cable 70 is preferably anchored in place in the prong member, as by lead 71, and extends upwardly through the bores of the prong member and collet hanger. The upper end of the cable 70 is connected to the switch member 18, next to be described.

The Pressure Switch and Locator As illustrated in FIG. 8, the pressure switch and locator unit 18 comprises a generally cylindrical housing 75, having an undercut upper portion 76 engageable by a suitable fishing tool.

The cable 70 extends upwardly through the bottom of the housing, and is anchored thereto, as by lead 77. A plurality of batteries 78 are circumferentially disposed around the inner wall of the housing, and are insulated therefrom by insulation 79. The batteries 78 rest with their lower negative terminals in electrical contact with an annular metallic plate 80 connected to the insulated Al wire 68. A similar annular metallic plate, or contact, 81 is in electrical engagement with the positive terminals of batteries 78.

A switch rod 82, disposed axially of the housing, is biased downwardly by spring 83 which is confined between an inwardly extending annular flange 84 of the housing and an outwardly extending circular flange 85 on the switch rod. As seen in FIG. 8, the downward movement of switch rod 82 is limited by the abutment of the rod flange 85 with the inwardly extending flange 86 of the housing. In this position, the lower end of switch rod 82 is below the terminal plate 81. A circular switch contact 87, mounted on the lower end of switch rod 82, is insulated therefrom by insulation 88. The diameter of the switch contact 87 is greater than the internal diameter of the terminal plate 81, so that whenever the switch rod 82 is moved upwardly, the switch contact 87 will engage the terminal plate 81.

The housing 75 is longitudinally slotted, as at 89, to receive a trigger arm 90 therein. Two such trigger arms are provided at diametrically opposite points, each being pivotally mounted to the housing by shear pins 91. The bottom end of each trigger arm is pivotally connected by a shear pin 92 to link 93 which, in turn, is pivotally connected to the switch rod 82. The upper ends 94 of the trigger arms 90 extend upwardly from the housing, and are adapted to slidably engage the inner wall of the tubing string 11.

The wire line 16, Which is controlled from the top of the well, passes downwardly through the top of the housing 75 and is secured therein by attachment to spool 95.

Operation The operation of the devices has been described in general terms above, and will now be described in detail.

The gun hanger assembly is first assembled at the top of the well, with the perforator gun 15 charged and connected to the extension hanger 14. This assembly is then connected to a running tool (not shown) and run down the well tubing 11 by wire line until the extension hanger is landed in the landing nipple 13, with the faces 41 of the locating levers 37 being engagement with the annular shoulder 42 of the landing nipple. The expander sleeve 33 is then jarred downwardly to force the locking dogs 31 outwardly into locked engagement with the locking groove 32 of the landing nipple. The running tool is now disengaged from the extension hanger and pulled from the well, as described in the above mentioned Patent No. 2,798,559.

The depth of the bottom of the tubing string 11 and the depth of the point at which it is desired to perforate are both known, and a suitable length electrical cable 70 is chosen in correspondence to the distance between these depths and used to suspend the detonator 17 from below the pressure switch 18. The pressure switch is then run into the tubing by wire line 16.

After reaching the upper end of the extension hanger 14, the lower end of the prong 62 enters the bore 45 of the extension hanger and passes downwardly therethrough to engage the inwardly projecting lower ends of the locating levers 37. The levers are pivoted out of engagement with landing nipple shoulder 42 and the prong continues downwardly until the detonator 67 comes into contact with the upper end of the prima cord 56. The guide member 53 will be forced slightly downwardly, and spring 54 acts thereagainst to hold the end of the prima cord 56 tightly against the detonator.

During this downward movement, the collet hanger fingers 64 pass over the flanged upper end of the extension hanger and the finger surfaces 66 engage the undercut portion 34 of the extension hanger.

It is to be noted that the detonator is now in contact with the perforator gun for the first time, which thus prevents any misfiring at any time previous to this connection at the bottom of the tubing.

The wire line 16 is now jerked upwardly to pull the expander sleeve 33' upwardly to allow the locking dogs 31 to retract, again in a manner fully described in the above mentioned Fredd patent, causing the extension hanger to be released from the landing nipple so that it is now free to move downwardly therethrough. The pressure switch 18 is lowered by the wire line, with the detonator, extension hanger and perforator gun being suspended therebelow by the cable '70, until the trigger arms 90 of the pressure switch 18 are below the bottom of the tubing string 11. A will be noted in the dotted line position of FIG. 8, when the trigger arms 9% are unrestrained by the tubing wall, spring 83 will move the switch rod 82 slightly downwardly to bring links EN) and 93 into alignment so as to pivot the upper ends 94 of the trigger arms outwardly.

When it is desired to discharge the perforator gun, the entire assembly is pulled upwardly by the wire line 16 until the trigger arms engage the lower end of the tubing string. Continued upward pulling on the wire line causes pivotal movement of the trigger arms around pins 9 1 to raise the switch rod 82 until the contact plate 87 thereon engages terminal plate 81 to complete the electrical circuit to the detonator 67. The detonator immediately explodes and ignites the prima cord 56 which, in turn, discharges the perforator gun in a conventional manner.

It is to be noted that at the time the trigger arms 90 have caused the electrical circuit to becomplete, that the bottom of the well tubing is substantially unrestricted, thus allowing the expanding gases, resulting from the firing of the perforator gun, to pass freely up the tubing. This, of course, prevents undue concussive stresses from being set up in the casing, tubing or packers therebetween.

It is also an important feature of this invention that the time of discharge of the perforator gun may be controlled from the top of the well and yet the only amount of relatively expensive electrical cable required is that used to connect the switch 18 with the detonator 67.

The entire assembly may be withdrawn from the well by a continued application of an upward pull on the wire line 16. This pull will cause the trigger arms 90 to first shear the shear pins 91, and then shear pins 92, permitting the trigger arms to fall to the bottom of the well. The entire assembly is then drawn upwardly through the tubing string to the top of the well, where the units are disassembled for later use.

As may be appreciated from the foregoing, the method and apparatus of this invention provide a positive surface control of the time and place of perforation. The construction of the switch member prevents the switch contact from closing, as long as the trigger arms 99 are within the tubing string, and thus, premature discharge of the perforator is prevented. The switch contacts can only be closed after the switch member is lowered completely beyond the end of the tubing string and after the switch member is then raised into proximity to the bottom of the tubing. This reversal in direction of movement of the wire line 16 affords a positive control from the top of the well as to the time of perforation. Furthermore, since the switch contacts are closed only when the switch member is in proximity to the bottom of the tubing, then the point of perforation is a function solely of the preselected length of cable 70 suspending the perforator from the switch member.

It is to be understood that the form of the invention, herewith shown and described, is to be taken as a preferred embodiment of the same, and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the attached claims.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. The method of perforating an oil well at a predetermined distance below the bottom of the tubing string therein which comprises: suspending a perforator in said tubing string adjacent the bottom thereof; connecting a locator member to said perforator at said predetermined distance thereabove while said perforator is suspended in said tubing string; lowering said locator member and perforator as a unit to below the bottom of said tubing string; raising said locator member into proximity with the bottom of said tubing string; and firing said perforator when the locator member is proximate to the bottom of the tubing string.

2. The method of perforating an oil well at a predetermined distance below the bottom of the tubing string therein which comprises: suspending a perforator in said tubing string adjacent the. bottom therof; connecting a locator member to said perforator at said predetermined distance thereabove; lowering said locator member and perforator as a unit to below the bottom of said tubing string; raising said locator member into proximity with the bottom of said tubing string; firing said perforator when the locator member is proximate to the bottom of the tubing string; and maintaining the bore of said tubing string substantially unobstructed during such firing.

3. The method of perforating an oil well at a predetermined distance below the bottom of the tubing string therein which comprises: suspending a perforator in said tubing string adjacent the bottom thereof; connecting a switch member to said perforator at said predetermined distance thereabove; lowering said switch member and perforator as a unit to below the bottom of said tubing string; raising said switch member into proximity with the bottom of said tubing string; and firing said perforator when the switch member is proximate to the bottom of the tubing string.

4. The method of perforating an oil well at a predetermined distance below the bottom of the tubing string therein which comprises: suspending a perforator in said tubing string adjacent the bottom thereof; connecting a switch member to said perforator at said predetermined distance thereabove; lowering said switch member and perforator as a unit to below the bottom of said tubing string; raising said switch member into engagement with the bottom of said tubing string; actuating said switch member by said engagement; and firing the perforator in response to such switch actuation.

5. The method of perforating an oil well at a predetermined distance below the bottom of the tubing string therein which comprises: suspending a perforator in said tubing string adjacent the bottom thereof; connecting a switch member to said perforator at said predetermined distance thereabove; lowering said switch member and perforator as a unit to below the bottom of said tubing string; raising said switch member into engagement with the bottom of said tubing string; actuating said switch member by said engagement; firing the perforator in response to such switch actuation; and maintaining the bore of said tubing string substantially unobstructed during such firing.

6. The method of perforating an oil well at a predetermined distance below the bottom of the tubing string therein comprising: suspending a perforator in said tubing string near the bottom thereof; suspending a detonator at said predetermined distance below a switch member; lowering said switch member down through said tubing string until said detonator comes into detonating engagement with said perforator; lowering said switch member, detonator and perforator through said tubing string to below the bottom thereof; raising said switch member, detonator and perforator until the switch member comes into engagement with the bottom of said tubing string; actuating said switch member by said engagement; and firing said perforator in response to the actuation of said switch member.

7. The method of perforating an oil well at a predetermined distance below the bottom of the tubing string therein comprising: locking a perforator gun in said tubing string near the bottom thereof, suspending a detonator said predetermined distance below a switch member, connecting said detonator in detonating relation to said perforator gun when the latter is locked in said tubing string, unlocking said perforator gun for downward movement thereof, lowering said switch member, detonator and perforator gun as a unit to below the bottom of said tubing string, raising the unit back toward the bottom of said tubing string, and firing the perforator when said switch member comes into adjacency with the bottom of said tubing string.

8. The method of perforating an oil well at a predetermined distance below the bottom of the tubing string therein, comprising: locking a perforator gun in said tubing string near the bottom thereof, suspending a detonator said predetermined distance below a switch member, connecting said detonator in detonating relation to said perforator gun when the latter is locked in said tubing tstring, unlocking said perforator gun for downward movement thereof, lowering said switch member, detonator and perforator gun as a unit to below the bottom of said tubing string, raising the unit back toward the bottom of said tubing string, firing the perforator when said switch member comes into adjacency with the bottom of said tubing string, and maintaining the bore of said tubing string substantially unobstructed during such firing.

9. The method of perforating an oil well at a predetermined distance below the bottom of the tubing string therein which comprises: locking a perforator in said tubing near the bottom thereof; suspending a detonator at said predetermined distance below a switch member; lowering said switch member down through said tubing; connecting the detonator in detonating engagement with said perforator; unlocking said perforator from said tubing; lowering said switch member, detonator and perforator as a unit downwardly through said tubing to below the bottom thereof; raising said switch member, detonator and perforator as a unit until said switch member is adjacent the bottom of said tubing; and firing said perforator when said switch member is adjacent the bottom of said tubing.

10. The method of perforating an oil well at a predetermined distance below the bottom of the tubing string therein which comprises: locking a perforator in said tubing near the bottom thereof; suspending a detonator at said predetermined distance below a switch member; lowering said switch member down through said tubing; connecting the detonator in detonating engagement with said perforator; unlocking said perforator from said tubing; lowering said switch member, detonator and perforator as a unit downwardly through said tubing to below the bottom thereof; raising said switch member,

detonator and perforator as a unit until said switch member is adjacent the bottom of said tubing; firing said perforator when said switch member is adjacent the bottom of said tubing; and maintaining the bottom of said tubing string substantially unobstructed during firing of said perforator.

11. The method of perforating an oil well at a predetermined distance below the bottom of the tubing string therein which comprises: locking a perforator in said tubing near the bottom thereof; suspending a detonator at said predetermined distance below a switch member; lowering said switch member, said detonator and a battery down through said tubing; connecting the detonator and battery in detonating engagement with said perforator; unlocking said perforator from said tubing; lowering said switch member, detonator and perforator as a unit downwardly through said tubing to below the bottom thereof; raising said switch member, detonator and perforator as a unit until said switch member is adjacent the bottom of said tubing; closing said switch when in adjacency to the bottom of said tubing; and firing said perforator when said switch member is closed,

12. An apparatus for perforating wells at a predetermined distance below the bottom of the well tubing therein, comprising: a locator member adapted to be lowered by wire line through said well tubing to below the bottom thereof, trigger means on said locator member engageable with the bottom of said well tubing upon up ward movement of said locator member back to the bottom of said well tubing, a cable extending downwardly from said locator member and having a length approximately equal to said predetermined distance, a perforator gun suspended from the lower end of said cable, and means to discharge said perforator gun upon engagement of said trigger means with the bottom of said well tubing.

References Cited in the file of this patent UNITED STATES PATENTS 2,192,591 Alexander Mar. 5, 1940 2,462,305 Catlin Feb. 22, 1949 2,476,136 Doll July 12, 1949 2,476,137 Doll July 12, 1949 2,495,431 Thompson Jan. 24, 1950 2,570,565 Lamb Oct. 9, 1951 2,636,561 Harrison Apr. 28, 1953 2,644,519 Kanaday July 7, 1953 2,679,899 Osborn June 1, 1954 2,705,920 Kanaday Apr. 12, 1955 2,741,316 Long Apr. 10, 1956 2,766,828 Rachford Oct. 16, 1956 2,859,697 Long Nov. 11, 1958 2,876,843 Huber Mar. 10, 1959 2,896,721 Cannaday July 28, 1959 

